Marine tankers



July 10, 1962 E. c. B. coRLETT MARINE TANKERS 3 Sheets-Sheet 1 Filed April l, 1958 mM, WM Nm. Nm,

Inventor a- @me July 10, 1962 E. c. B. CORLETT 3,043,256

MARINE TANKERS Filed April 1, 195e s sheets-sheet 2 A torneyg July 10, 1962 Filed April l, 1958 E. C. B. CORLETT MARINE TANKERS 5 Sheets-Sheet 3 llll Illl j 54 Inventor m m Bwraf A ttorneg Unite 3,043,256 MARINE Taramas Ewan Christian Brew Cox-lett, Worting, near Basingstoke,

England, assigner to Wm. Cory & Son Limited, London, England Filed Apr. 1, 1958, Ser. No. 725,674 Claims priority, application Great Britain Apr. 5, 1957 6 Claims. (Cl. 114-74) States Etaient The carirage of liquid methane by ship poses several i problems due to the fact that the density of liquid methane is very low compared with that of water, and that the methane must be insulated from ambient heat to prevent excessive evaporation. From the point of view of insulation, it is best for all the methane tankage `to be below deck, but such a vessel would have an undesirably high eeboard. This difficulty can be cured in some respects by the provision of additional tanks supported on the deck of the ship, but although this reduces the freeboard to a workable level and allows the methane-capacity of the ship to be increased, such deck tanks require very special supporting means to retain them firmly in position on a rolling deck, and also require special insulation from am- -bient'heat due to their exposed position. This is particularly troublesome in a tanker of, say, 16,000 tons which has to operate in rough seas and in hot climates. Ari object of the present invention is to enable a methane tanker to carry as much methane as possible and, at the same time, avoid the disadvantages given above.

According to the present invention, there is provided a marine tanker for the bulk transport in the liquid state at low temperature of methane (or like ordinarily-gaseous substances), wherein the cargo tanks comprise a plurality of main tanks disposed in a closely-spaced row along the fore-and-at centre line of the ship which main tanks are of circular cross-section in plan and extend at their widest parts for substantially the full width of the ship, together with comparatively small wing tanks provided in the spaces between the main tanks toward the sides of the ship, and wherein the wing tanks are wholly below the main deck while the main tanks have portions of reduced diameter which extend up through the main deck the protruding portions of the main tanks being enclosed in a longitudinally-extending turret structure above the main deck.

In this way a kind of turret ship is formed, and this construction provides several advantages. The entire methane tankage is below deck so that it can be insulated more effectively, and the problem of supporting tanks on the deck is removed. At the same time, the -freeboard is not raised to an unworkable level, and the handling qualities of the ship are not impaired.

The tops of the main tanks may have narrow necks projecting up through the turret, and, when loaded, each tank is ordinarily kept topped up to a level within the narrow neck. This means that, under normal working conditions, the liquid-free surface in each tank will not be so large as to atleet adversely the stability and control of the ship, particularly in rough seas.

The above and other features of the invention will be apparent in the following description, given by way of example, of one embodiment in accordance with the invention, reference being had to the accompanying drawings in which:

'ice

FIGURE 1 shows in elevation a marine tanker for the transport of methane,

FIGURE 2, is a plan showing the arrangement of the methane tanks in the holds,

FIGURE 3 is a further plan showing the arrangement of tanks at main deck level, and

FIGURES 4 and 5 are transverse views partly in section seen on the lines 4-4 and 5-5 respectively of FIGURE 3.

Referring iirstly to FIGURES l and 2, the cargocarrying section of the tanker hull 10 is divided into six separate main hold compartments 11 to 16 `by a series of transverse bulkheads 17. Disposed individually in the hold compartments 11 to 16, in a closely-spaced row along the fore-and-aft centre line of the vessel are six heavilyinsulated main cargo tanks 18 and 23. The tank insulation is shown at 60 in FIGURE 4. These main tanks are, for the roost part, substantially cylindrical in form with their principal axes vertical, and in general they extend -at their widest parts for substantially the whole width of the vessel although tanks 19 and 23 are somewhat less in diameter than tanks 20, 21 and 22, and the most forward tank 18 is a good deal less still in diameter.

The vessel is of turret construction, that is to say it has a main deck at the level 24 and a narrower turret deck above at the, level 25. Each of the main tanks 18 to 23 extends up lthrough the main deck at level 24, and, with the exception of the tank 20, the portions of the tanks that protrude above the main deck are as large in diameter as can be conveniently accommodated within the turret structure 26. To this end, tanks 19, 21, 22 and 23 have stepped-in upper portions 28, 29, 30 and 31, but the forward tank 18, being already relatively narrow, does not need to be stepped in. Each of the six tanks terminates at its upper end in a narrow neck 27 surmounted by a pump' motor housing 32. In the case of the iixe tanks 18, 19, 21, 22 and 23 the narrow tank neck 27 reaches up through the turret deck at level 25and the housing 32 is situated on said deck, but the tank 20, for reasons which need not be discussed here, is not as high as the other five, having its neck 27 terminating only just -above the main deck level 24 and its pump motor housing 32 disposed on the main deck within the turret structure.

Owing to the circular plan form of the main tanks 1S to 23, there is an appreciable space below deck-s between one tank and the next at opposite sides of the vessel, and in the lcase of tanks 19 to 23 these spaces between are utilised by disposing in them eight additional insulated wing tanks 33 of much smaller capacity bearing insulation 61 (FIGURE 5). The wing tanks 33 are all cylin- V drical with their principal axes upright, and are located the bulkheads17 branching, as it were, into two diverging bulkhead-S 35 to embrace a wing tank as it approaches each side of the hull.

It will be observed that each of the small wing tanks 33Y has a diameter only about one-iifth the beam of the ship, and, as can be seen in FIGURE 3, the turret structure 26 and turret deck 25 have a width which is about 60% of the ships beam. In a typical example of a 16,000 ton deadweight methane tanker, the Ilargest main cargo tanks might have a capacity of the order of 280,000 cubic feet, and the wing tanks a capacity of 9,000 cubic feet each. In a vessel of this order of size the turret width of -ap-A prox-imatcly 60% of the beam aitords a working deck on either side that is wide enough for easy working.

As can best be seen in FIGURE 3, the spaces within the" turret structure 26 and between the portions of the main cargo tanks lying therein, are occupied by a cargo liquei the ship will have an easy motion in rough seas.

faction plant and by tanks Si) on the main deck. Thus Athere tanks Si) between the pairs of methane tanks 18 and 19, 21 and 22, and 22 and 23, with an additional smaller tank beyond the aft methane cargo tank 23, while between the cargo tanks 19 and ,21 and over the-methane cargo tank 20 there is a further large tank 80. Despite the heavy insulation of the methane cargo tanks, there will be a certain amount of methane boiling o in them during a voyage, and gaseous methane drawn olt'fr'om the tanks can be reliqueled lso that it can be returned to the tanks and the liquid level kept up. Eachfmain tank to 23 is normally kept topped up so that the liquid level is in the comparatively narrow neck 27, whereby both the Y ving the hold will freeze around the leak and stop it. The

ballast tanks S0 are simply constructed of welded plate,

land are rectilinearly-shaped as shown lin'FIGURE 3,

being multi-sided -so as to best lill the'available spaces.

In addition to the methane cargo tanks, land the deck tanks 80, the vessel also has, besides further conventional ballast which will not be described in detail, a number of deep tanks 82, 83. The deep tanks S2 are inthe fore part of theship, grouped around the fore-most methane tank f -18,-while the tanks S3 are grouped around the aft methane tank 23. The deep tanks 82, 83 may be lled with water ballast, but preferably they are'used for' the' Ytransport of an oil cargo, in addition to the liquid methane cargo. In a ship of 16,000 tous deadweight these tanks together with the deck tanks S0 can carry about 9,30) tons of oil cargo,

.Which'is a valuable supplement tothe liquid methane cargo.

l. A marine tanker for the bulk transport of liquid methane at low temperature andsubstantially atmospheric pressure comprising the combination vof'a hull, a main deck, a plurality of transverseV bulkheads dividing up the cargo space below the main deck into a plurality of separate main hold compartments, a turret deck narrower than the main deck and extending fore-and-aft above theV main deck over -allsa'id hold compartments, =a plurality of externally-insulated main tanks for liquid methane cargo, said tanks being disposed in :a closely-spaced row one in each of Vthe hold compartments and each tank being stepped in at at least one level near the top thereof so as to give the tank a narrow neck portion with the full-width portion of the tank disposed wholly below the main deck land the narrow neck portion projecting above the main deck and lying Within the conlines ofthe portion of the deck width defined between the sides of the turret deck, and a plurality of smaller externally-insulated wing tanks -for lliquid methane cargo said wing tanks being disposed wholly below the main deck in wing spaces between the ,main tanks toward the sides of the ship and said transverse bulkheads being formed around said Vwing tanks to venclose each wing tank in its own separate wing hold i' deck, a plurality of transverse liquid-,tight bulkheads dividing up the cargo space below the main deck into a plurality of separate main hold compartments, a turret deck narrower than the main deck and extending foreand-aft above the main deck, a plurality of externallyinsulated main tanks for liquid methane cargo each having a coniiguration that is mainly of upright cylindrical form, said tanks being displaced in a row one in each of the hold compartments and each tank being stepped in at at least one level nea-r the top .thereof so as to give the tank a narrow neck portion, and a plurality of smaller externally-insulated wing tanks for-liquid methane cargo, said wing tanks being disposed wholly below the main deck in wing spaces between the main tanks toward the sides of the ship and said transverse bulkheads being formed around said wing tanks to enclose each wing tank in its own separate wing hold compartment.

3. A marine tanker for the bulk transport ofy liquid methane at low temperature and substantially atmosphere pressure comprising the combination of ahull,fa main deck, a plurality of transverse liquid-tight bulkheads dividing up the cargo spiace below the main deck into a plurality of separate main hold compartments, a'V turret deck narrower, than the main deck and extending foreand-aft above the-main deck in uninterrupted manner over all said hold compartments, turret side structure kenclosing the space between the main and turret decks, a

Vplurality of externally-insulated main tanks for liquid methane cargo each having a configuration that is mainly of upright cylindrical form and Aoccupies at its widest part substantially the whole available width of the vessel, said tanks being disposed-in a closely-spaced row one'in each of the hold compartments with their upright axes intersecting the ore-and-aft centre line of the vessel and each tank being stepped in at at least one level near the top thereof solas tol .give 'the tank at centrally-placed narrow neck portion with the lfull-diameter portion of the tank disposedwholly below thermain deck and the central neck portioneprojecting above rthe main'v deck and lying within the confines of the portion of the deck width dened by the turret structure, at least some of said main tanks having between the neck vva-nd the ull-diameter portion -a stepped section of an intermediate diameter which f intermediate diameter stepped section` commences just spaces between the main tanks toward the sides ofthe ship and said transverse bulkheads being formed around said wing tanks to enclose each wing tank in its own separate wing hold compartment.

4. A tanker Ias claimed in claim 2, wherein at least some of the main tanks each have, between the neck and Ithe yfull'diameter portion, a stepped section offan intermediate diameter, which stepped section commences just below the main deck but is otherwise located wholly within the turret and of a'diameter as llargeasthe space within the turret structure will allow.

5. A tanker ,as claimed inclaim 4, wherein deck ballast or oil cargo tanks are disposed in the turret between the intermediate diameter sections of the cargotanks.

6. A tanker as claimed in'cla'im 2, wherein' the wing tanks are of upright cylindrical Aform' .andV each' has a diameter approximately one fifth of thel beam of the ship.

References Cited in the tile of this patent UNITED STATES PATENTS 666,076 Mason et a1 tan.- 15, 190i 1,085,086 Jackk f .f Ian.- 20,' 1914 1,111,740 Frear Sept. 29, 1914 (Other references on following page) U UNITED STATES PATENTS Bittlestone et al. Oct. 22, 1918 McLaughlin June 10, 1952 Blomeley May 22, 1956 schnellhardt sept. 24, 1957 5 6 Beckwith Nov. 11, 1958 Rupp Aug. 4, 1959 FOREIGN PATENTS France Nov. 18, 1953 

